1. Field of the Invention
The present invention relates to a method of forming an interlayer insulation film used for multilayer interconnects and particularly relates to a method of forming an interlayer insulation film having a low dielectric constant, high mechanical strength, and low water-repellency.
2. Description of the Related Art
In semiconductor integrated circuits, miniaturization has been pursued in response to demands on increased chip speed and performance. In the past, aluminum had been used as a material for multilayer interconnects. As interconnects had become minute and long, current densities had increased relatively, causing electromigration during use. Because aluminum has comparatively high electric resistivity, a problem with signal delay also occurred.
Consequently, copper having high resistance to disconnections and comparatively small electric resistivity was brought to attention in place of aluminum. In 1997, Cu trench filling interconnect technology called “Dual-Damascene” was developed by IBM and Motorola. Different from conventional methods in which an interlayer is filled with an insulation film after an interconnect is formed by processing an AI film convexly by etching, in this technology, an interconnect is formed by: An interlayer insulation film is trench-etched, a Cu thin film is electroplated/deposited on the entire surface, the copper is polished by the Chemical Mechanical Polishing (CMP) process so that the copper remains only in a trench portion.
In the Damascene interconnect technology, application of a low-k insulation film is essential for solving signal delay problems. As low-k insulation films, there are, for example, an inorganic SOG (silicon oxide glass) film deposited by a spin coat process, a fluorinated amorphous carbon film deposited by plasma CVD using CxFyHz as a source gas, or a SixCyOx film deposited by plasma CVD using silicon hydrocarbon as a source gas and others. Of these low-k films, the SixCyOx film is most preferable as it possesses both a low dielectric constant and mechanical strength.